Visualization of nuclear components has introduced new dimensions to the biology of the nucleus and new insights into its chemistry. The most common dye used to make DNA or RNA bands visible for agarose gel electrophoresis is ethidium bromide. It fluoresces under UV light when intercalated into the major groove of DNA (or RNA). In the case of DNA, this is usually double-stranded DNA from PCR'S restriction digests, etc. Single-stranded RNA can also be detected, since it usually folds back base pairing for the dye to intercalate. By running DNA through an ethidium bromide-treated gel and visualizing it with UV light, any band containing more than ˜20 ng DNA becomes distinctly visible.